The present invention is directed to a device for ignition of an internal combustion engine.
Devices for ignition of an internal combustion engine, in which a computer and an ignition output stage are provided, are conventional. The computer calculates a charge starting point, at which the ignition output stage begins to control a current flow through the primary side of the ignition coil. In conventional ignition devices, an ignition instant, at which the ignition output stage is switched into a non-conductive state, is also output by the computer.
The device according to the present invention for ignition of an internal combustion engine has the advantage that the ignition occurs independently of the computer if a preset primary current value is exceeded, i.e., the ignition energy is controlled by reaching the desired shutoff current and is not a function of the output of a dwell period or dwell angle. For this purpose, only a charge starting point must be output by the computer. The computer is therefore not burdened by also outputting an ignition instant in addition to the charge starting point. The computing capacity of the computer may therefore be used for other calculations.
A flip-flop may be used as a convenient means for triggering the ignition output stage, the set input being connected to an output of the computer. In this case, the reset input of the flip-flop may be used to trigger the ignition. An example embodiment of the arrangement for detecting the current flow through the primary coil has a resistor and a comparator having a reference voltage. The signal of the comparator or other circuit parts, e.g., a unit for detection of the spark current on the secondary coil of the ignition coil or a unit for detection of the collector voltage of the ignition output stage, may be used to analyze the ignition instant.